How does satellite navigation work?
Networks of over 20 GPS Global Positioning Satellites (GPS) orbit the Earth twice every day approximately 12,000 miles above the Earths surface. They are positioned so that a minimum of 4 satellites are visible at any one time, with most navigation systems requiring a minimum of three GPS satellites to calculate its position. All Sat Nav devices use a GPS receiver to calculate their position on the surface of the Earth. This is then overlaid onto a local road map showing you your position to within 10 metres.
Fully fitted navigations systems can also use gyroscopic sensors and the vehicles speed information to continue navigating even if GPS reception is lost (by travelling through a tunnel or in a built up area etc)
Software can then calculate the 'best' route between two points, using average road speed data with other parameters such as shortest route, avoid motorways, avoid toll roads etc.
All units give voice instructions for route guidance, for instance: "At the roundabout take the second exit", while many use a colour screen to show a schematic illustration of the road ahead. This can usually be displayed in a number of ways including 2D, 3D and day and night modes.
Many units now allow you to input your destinations full postcode, which is far quicker than having to enter in a full address.
Most units are now operated by using a touching the screen making using the devices simple and intuitive.
What route options do Sat Navs offer?
The majority allow you to select from a range of options, such as the quickest or shortest route, or choose via a particular waypoint or one avoiding tolls road. Most will also allow you to view the route before you commence and can offer an alternative route if you do not wish to take the initial route suggested.
How easy are they to set up?
The portable devices work 'straight out of the box' with no fitting required, other than a support bracket on the windscreen and a cigarette lighter power source. Most also contain a rechargeable power source so they can be used outside of the car. Some navigation systems also contain features such as speed camera locations. In order to keep this database up to date you will need access to a computer with internet access. A subscription may also be required to access this data.
Phone-based devices vary, and you may need to upgrade your phone and/or contract in order to use navigation software.
Fully installed navigation systems, such as Kenwood & Alpine, require professional installation but do offer outstanding navigation capabilities.
Do I need to install an aerial into my car?
No. All of the portable sat navs include an integral antenna to receive the GPS signal that gives the unit its location. The only exception would be if your vehicle has metal elements or a heat reflective windscreen. An external antenna may then have to be used.
Fully installed navigation systems are provided as standard with an internal GPS antenna.
Can I take use the unit abroad?
Most sat navs are available “off the shelf” with European or even North American mapping as standard. Those units supplied with only UK mapping are usually upgradeable, which means you can buy extra mapping when you need it.
Assuming you have the correct map software, the unit will work in any car, in any location.
What about traffic information?
With most units, traffic information is an optional extra, paid for via a monthly or annual subscription.
If your driving does not encounter much congestion it may be an unnecessary expense. Also, if the congestion 'hot spot' is a daily occurrence (as opposed to a tailback behind an accident) it may not be flagged on your route.
Are speed camera detectors legal to use in the UK?
There are three types of camera detectors. GPS-based units that simply alert you to the location of fixed cameras, the system commonly used by sat navs, are legal. The accuracy of these units is solely down to the software available, as they do not “detect” the speed cameras, but merely know where they are. If using your navigation device as a speed camera locator is a high priority ensure that you choose one with a reliable database.
Jammers, which send a laser signal to the speed detector preventing it from taking a reading are illegal, and their use could lead to prosecution for perverting the course of justice (among other things).
The third type of unit, which picks up the radar signals emitted by cameras and laser signals sent by mobile camera vans, is currently legal but is expected to be outlawed later in the year by the new Road Safety Act.
Can the mapping be updated?
All sat-nav devices rely heavily on their mapping data. As with an atlas, when the road network changes, the mapping also needs to change. This is even more important in advanced devices which can also navigate by points of interest and shops and businesses.
Generally speaking, the portable units can be updated through connection to an internet-connected PC or by purchasing an SD card with the new mapping loaded onto it, while the phone-based devices can download an update through their GPRS connection. To update a fully fitted system you usually need to buy a data DVD from an authorised dealer, although some of these systems are now upgradeable via the internet
What are Points of interest?
Most Sat Navs contain a large amount of points of interest (POI) information, such as Airports, petrol stations and parking. Having a list of POI stored in your sat nav makes it easy to find the hotel or restaurant that you’re looking for, even if you don’t know the address.
